Many people have pointed out that it is a problem for the security of Bitcoin if any of the mining pools gains over 50% of total mining capacity.

I am wondering, could existing antitrust statutes (such as the Sherman Antitrust Act in the US) be used to forcibly break up such large pools? After all, a majority pool could be considered to be a kind of "monopoly" and to be "anticompetitive."

If a given pool grows too large, other miners could file a complaint with the Department of Commerce of whatever country that particular pool is based in. The existing civil regulatory procedures could take over from there. Or, a civil suit could be filed in the courts to force faster action.

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It is not a real security issue. With less than 50 % you can't attack bitcoin.

With more, the chances get higher that you can create a mess. But you need a lot more than 50 % to do a serious attack. And the most serious attack possible is to revert transactions. You cannot steal bitcoins, because even if you own every single mining machine, you cannot change that ECDSA signatures are necessary for valid spending.

Many people have pointed out that it is a problem for the security of Bitcoin if any of the mining pools gains over 50% of total mining capacity.

Its not really such a big problem if a mining pool gains over 50% of the total mining capacity. Its not a desirable situation, but the mining power is not from the pool, and so if the pool started cheating the people connecting to the pool would change to another one.

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I am wondering, could existing antitrust statutes (such as the Sherman Antitrust Act in the US) be used to forcibly break up such large pools? After all, a majority pool could be considered to be a kind of "monopoly" and to be "anticompetitive."

In general, so-called "antitrust" laws and other regulations are not used to attack abusive companies, but to defend the position of abusive companies and hurt competition.

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If a given pool grows too large, other miners could file a complaint with the Department of Commerce of whatever country that particular pool is based in. The existing civil regulatory procedures could take over from there. Or, a civil suit could be filed in the courts to force faster action.

Your suggestion is based on the assumption that laws governing corporations affect mining pools. They do not. However, I would like to see a voluntary agreement of pool operators to cull newer users to avoid going over 50%. Being the internet, there is no way to make this binding of course. Perhaps random DDoS will do the job for us, who knows.

Many people have pointed out that it is a problem for the security of Bitcoin if any of the mining pools gains over 50% of total mining capacity.

I am wondering, could existing antitrust statutes (such as the Sherman Antitrust Act in the US) be used to forcibly break up such large pools? After all, a majority pool could be considered to be a kind of "monopoly" and to be "anticompetitive."

If a given pool grows too large, other miners could file a complaint with the Department of Commerce of whatever country that particular pool is based in. The existing civil regulatory procedures could take over from there. Or, a civil suit could be filed in the courts to force faster action.

Please cite precisely how the sherman antitrust act could be applied. Merely having the majority market share does not make for an illegal monopoly - it invites tighter regulation sure, but it does not mandate breaking up.

This is a very interesting question. I had to think about it for awhile, do some research and think some more. From my prospective the short answer is yes.

Section 2 of the Sherman act deals with monopolization making it unlawful to monopolize, attempt to monopolize, or conspire to monopolize. The US Supreme Court has held that any market share of 50% or higher is sufficient to be of concern. Additionally the willful acquisition or maintenance such as a conscious acts designed to further or maintain a monompoly market share will violate section 2 of the Sherman act. What is clear is that the statute does not require that monopoly power be abused or intentionally exercised to drive out competition, although such conduct, if present, is sufficient to make out a violation.

Now with that said is it likely? Hell no!! First, it would be very cost prohibitive. Second, as most pools are not in the US the law is irrelevant. Sure other countries have anti competition laws how they would apply Im not sure. Thats is to say a nongovernmental entity. Now if a government was to take action, that is plausible but unlikely at the stage. Maybe in 10 or 15 years the landscape might be more accomidating to such action.

This is not ment to be legal advice. I post this to further the descussion.

Its not really such a big problem if a mining pool gains over 50% of the total mining capacity. Its not a desirable situation, but the mining power is not from the pool, and so if the pool started cheating the people connecting to the pool would change to another one.

In theory, I think a suitably malicious pool with over 50% of the total mining capacity might be able to reduce the amount of blocks that other pools mine, or even stop them from mining altogether - which would provide an incentive for more miners to switch to the malicious pool...

Section 2 of the Sherman act deals with monopolization making it unlawful to monopolize, attempt to monopolize, or conspire to monopolize. The US Supreme Court has held that any market share of 50% or higher is sufficient to be of concern. Additionally the willful acquisition or maintenance such as a conscious acts designed to further or maintain a monompoly market share will violate section 2 of the Sherman act. What is clear is that the statute does not require that monopoly power be abused or intentionally exercised to drive out competition, although such conduct, if present, is sufficient to make out a violation.

What conscious acts are you imagining? Absent conscious acts specifically intended to acquire or maintain a monopoly, there is no violation of section 2. If a monopoly naturally results just because someone provided a superior product or superior service, there is no violation of the Sherman act.

I'm pretty sure this is right - the miners don't get to choose block content in a pool. Right?So getting 50% of hash rate or miner count means nothing.

If a single pool ever gets more than 50% of the mining power, it can rewrite transactions by producing its own chain that contains alternate versions of those transactions. Their chain will ultimately be longer than everyone else's chain because they have more computing power. The pool manager decides what transactions go in the block -- the miners have no idea what the contents of the block they found will actually be until it's published. (They only get the headers.)

Imagine we're at block 150,000. I form two transactions, one to send 35 bitcoins to you and one to send them to someone else. I send the transaction to send those 35 bitcoins to you to the network. The networks commits it and you begin to get confirmations. But the mining pool has actually started working on a chain with the alternate transaction and is not sharing its blocks with the network. You get, say, 10 confirmations and decide to give me the goods. Then the mining pool sends its longer chain to the world. The transaction gets rewritten and everyone who found blocks after that transaction loses their bitcoins, as do you.

In theory, if you controlled 51% of the computing power, you could make 100% of the mining revenue, and have total control over what valid transactions are included in the chain, simply by ignoring everyone else's work. You still win.

I am an employee of Ripple.1Joe1Katzci1rFcsr9HH7SLuHVnDy2aihZ BM-NBM3FRExVJSJJamV9ccgyWvQfratUHgN

I don't think government involvement is the solution. We just need more competition in the form of more pools. Personally I think there should be around 10 public pools. That way no pool even gets close to the 50% mark. This would take effort from individuals willing to set up pools as well as willingness of miners to diversify more and embrace newer, smaller pools.

There are a lot of pools. Problem is, there is little reason to NOT use one of the biggest pools.

The top 3 all have something to recommend themselves. BTCguild can be low fee. slush is for those who like the luck aspect of bitcoining. And deepbit just works and works well (less than 1% rejects for me compared to 5%+ in other pools, e.g.).

The new pools just have a rough time getting off the ground. Except for multipool there are no advantages to any of the newcomers, and nothing but disadvantages. You could get a block from hell which takes 3 weeks to mine in a small pool. The operator may just say screwit and take all the earnings since they don't see a future in running their pool. And so on and so forth.

Now, if there were clear and obvious advantages to either solo mining or mining in a smaller pool we wouldn't have this centralization of power we see in our "distributed" network. At the moment the network consists of basically 3 nodes.

In theory, if you controlled 51% of the computing power, you could make 100% of the mining revenue, and have total control over what valid transactions are included in the chain, simply by ignoring everyone else's work. You still win.

I understand that. But isn't the pool still dependent on probability to write the block first?If a smaller pool finished a block first it would still propagate around the network. The larger pool can't stop that. I mean having > 50% of the miners doesn't mean it controls > 50% of the clients receiving blocks.

Or maybe I'm still missing something about that. In which case, I don't really see how being slightly less than 50% is different from being slightly more than 50%. If the bigger pool has a lucky streak it could create blocks quicker even with less than 50% of the hash rate. And in that case the system is potentially in failure mode now, and would seem to be poorly designed.

I understand that. But isn't the pool still dependent on probability to write the block first?

No.

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If a smaller pool finished a block first it would still propagate around the network. The larger pool can't stop that. I mean having > 50% of the miners doesn't mean it controls > 50% of the clients receiving blocks.

So what. It just ignores the block found by the smaller pool.

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Or maybe I'm still missing something about that. In which case, I don't really see how being slightly less than 50% is different from being slightly more than 50%. If the bigger pool has a lucky streak it could create blocks quicker even with less than 50% of the hash rate. And in that case the system is potentially in failure mode now, and would seem to be poorly designed.

With slightly more than 50%, you can simply ignore every other block. You will win eventually because your chain will eventually be longer. The only blocks on the public chain will be your blocks.

With less than 50%, you will fall further and further behind. You will be using up more and more resources with a lower and lower probability of success. You'd do much better to accept blocks found by other miners because it makes your chain longer and thus gives you a better chance of getting your own blocks into the chain.

(By the way, there is a fix to this attack that requires no change to the protocol. It has some issues though, but if this ever became a huge problem, it could be perfected and deployed.)

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(By the way, there is a fix to this attack that requires no change to the protocol. It has some issues though, but if this ever became a huge problem, it could be perfected and deployed.)

Ok. Well, I guess I still need to understand the mechanics of the block propagation more.

I'd say that the recent growth of deepbit is pretty concerning then. It would be wise to get attention before rather than after it reaches 50%. Especially since there was some report of botnets feeding into it. I don't have any idea who runs it but even if it's someone trusted by the community it would seem some sort of delegation/split of control would be healthy. Not that anything like that could be forced, of course. But it would make really nasty headlines if it could be demonstrated as weakness, and even worse if that was pulled off before the mitigation you mention could be deployed.

Whether or not it applies, sherman act suits are not things that happen very often. Getting a state's attorney office interested is going to be a non-starter. If there was a pool in jurisdiction that actually got attention along these lines, I'm sure they'd just move overseas overnight.

If you really wanted to attack a pool I'd suggest a tax or employment authority. I consider it very unlikely most pools are conducting themselves appropriately in regards to accounting, withholding and employment law.

Whether or not it applies, sherman act suits are not things that happen very often. Getting a state's attorney office interested is going to be a non-starter. If there was a pool in jurisdiction that actually got attention along these lines, I'm sure they'd just move overseas overnight.

If you really wanted to attack a pool I'd suggest a tax or employment authority. I consider it very unlikely most pools are conducting themselves appropriately in regards to accounting, withholding and employment law.

Miners are not employees of pools, at best you could argue they're contractors and paid in kind.

I can't see any way this would not be self-correcting. Participating in a mining pool is voluntary affiliation. As soon as the transactions started going awry, people would notice, pool miners too. Pool miners have an obvious vested interest in the stability of valid transactions; they are part of the bitcoin market. It would not be in their best interest to continue their affiliation. The pool would self-destruct.